Shawn Johnson, who won gold in Beijing, retires

Former Olympic gold-medalist Shawn Johnson announced her retirement from competitive gymnastics Sunday.

Johnson, who collected four Olympic medals and three World medals in her career, was attempting to comeback from a knee injury suffered while skiing in 2010, but decided to retire because of several setbacks.

"I still have the heart, drive and desire to compete and help the USA at the London Olympics," said Johnson. "Unfortunately, it has become obvious that my left knee is not able to sustain the demands of gymnastics any longer. All I can do now is gracefully retire and thank everyone who has believed in me and my journey."

Johnson helped Team USA claim its first-ever World team gold medal on foreign soil at the 2007 World Championships in Stuttgart, Germany. She then became just the fourth American woman to earn the World all-around gold medal.

She followed that performance by hauling in four medals at the 2008 Beijing Olympics, including a gold in balance beam, joining Shannon Miller in 1996 as the only two U.S. women to record that feat.

Johnson also earned the team silver along with individual silver medals in the all-around competition and floor exercise in Beijing.

She was recently invited to the American selection camp for the upcoming Summer Olympics in London, but decided to announce her retirement now "so the focus for the next three weeks will be on the incredibly talented gymnasts who are trying to make our 2012 Olympic Team."

"Shawn has been an outstanding representative of USA Gymnastics throughout her career," said Peter Vidmar, chairman of the Board for USA Gymnastics. "I have tremendous respect for Shawn's dedication and hard work during her return to gymnastics for a run at her second Olympics.

"And while we celebrate her competitive achievements, we also appreciate everything she has done as a role model and ambassador for our sport. We look forward to having her continue to be a part of the gymnastics movement while she pursues the next chapter of her remarkable career."

Johnson is considering college and volunteer work for her future plans and intends to still be involved in gymnastics, joining Team USA in London on behalf of some sponsors.